c++: Wrong error with alias template in class tmpl [PR104108]

In r10-6329 I tried to optimize the number of calls to v_d_e_p in
convert_nontype_argument by remembering whether the expression was
value-dependent in a bool flag.  I did that wrongly assuming that its
value-dependence will not be changed by build_converted_constant_expr.
This testcase shows that it can: b_c_c_e gets a VAR_DECL for m_parameter,
which is not value-dependent, but we're converting it to "const int &"
so it returns

  (const int &)(const int *) &m_parameter

which suddenly becomes value-dependent because of the added ADDR_EXPR:
has_value_dependent_address is now true because m_parameter's context S<T>
is dependent.  With this bug in place, we went to the second branch here:

      if (TYPE_REF_OBJ_P (TREE_TYPE (expr)) && val_dep_p)
        /* OK, dependent reference.  We don't want to ask whether a DECL is
           itself value-dependent, since what we want here is its address.  */;
      else
        {
          expr = build_address (expr);

          if (invalid_tparm_referent_p (type, expr, complain))
            return NULL_TREE;
        }

wherein build_address created a bad tree and then i_t_r_p complained.

	PR c++/104108

gcc/cp/ChangeLog:

	* pt.cc (convert_nontype_argument): Recompute
	value_dependent_expression_p after build_converted_constant_expr.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/alias-decl-74.C: New test.

diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index c350ebb..d47483d 100644 (file)
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -7316,7 +7316,7 @@ convert_nontype_argument (tree type, tree expr, tsubst_flags_t complain)
   if (non_dep)
     expr = instantiate_non_dependent_expr_internal (expr, complain);
 
-  const bool val_dep_p = value_dependent_expression_p (expr);
+  bool val_dep_p = value_dependent_expression_p (expr);
   if (val_dep_p)
     expr = canonicalize_expr_argument (expr, complain);
   else
@@ -7357,6 +7357,8 @@ convert_nontype_argument (tree type, tree expr, tsubst_flags_t complain)
          expr = maybe_constant_value (expr, NULL_TREE,
                                       /*manifestly_const_eval=*/true);
          expr = convert_from_reference (expr);
+         /* EXPR may have become value-dependent.  */
+         val_dep_p = value_dependent_expression_p (expr);
        }
       else if (TYPE_PTR_OR_PTRMEM_P (type))
        {

diff --git a/gcc/testsuite/g++.dg/cpp0x/alias-decl-74.C b/gcc/testsuite/g++.dg/cpp0x/alias-decl-74.C
new file mode 100644 (file)
index 0000000..8382d85
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/alias-decl-74.C
@@ -0,0 +1,9 @@
+// PR c++/104108
+// { dg-do compile { target c++11 } }
+
+template<template<const int&> class T>
+struct S {
+  static int m_parameter;
+  template<template<const int&> class TT>
+  using U = TT<m_parameter>;
+};